Electrostatic discharge (ESD) generated from static electricity is usually characterized by fast transient high voltage discharge. An ESD event can occur in electrical and electronic circuits, such as an integrated circuit. It can create sufficiently high voltage to cause destructive breakdown of devices connected to, for example, the inputs and/or outputs of the integrated circuits (ICs). Various ESD protection schemes have been introduced to protect the ICs from an ESD event. Silicon controlled rectifier (SCR) is typically used as one of the ESD protection schemes.
Crystalline-on-insulator (COI) substrates, such as silicon-on-insulator (SOI) substrates, are garnering interest since they have lower parasitic capacitance due to isolation from the bulk silicon. This improves power consumption. However, conventional SCR-based ESD protection components formed on bulk substrates are not compatible with SOI substrates. For example, the thin silicon surface layer of SOI substrate presents various challenges to introduce SCR-based ESD protection circuit in SOI substrate.
From the foregoing discussion, it is desirable to provide SCR-based ESD protection circuit which is compatible with complementary metal oxide semiconductor (CMOS) applications using SOI substrate. It is also desirable to have an ESD protection circuit integral within the IC to effectively protect sensitive input and/or output circuits from an ESD event.